1. Field of the Invention
The present invention relates generally to tracheal intubation, and more specifically to an airway catheter guide system for retrograde intubation.
2. State of the Art
Failure to maintain a patent airway for more than a few minutes can result in brain damage or death. Tracheal intubation is an essential procedure for maintaining a patent airway in patients receiving general anaesthesia for certain kinds of operations, for assisting ventilation in patients with ventilatory insufficiency, and to protect the lungs where protective reflexes of the larynx are inadequate. A categorized list of indications for this procedures is set forth as follows:
Upper airway obstruction PA1 Airway control PA1 Prevention of aspiration PA1 Inability to clear tracheobronchial secretions PA1 Need for mechanical ventilation
Foreign body PA2 Tumour PA2 Infection PA2 Laryngospasm PA2 Bilateral vocal cord paralysis PA2 Epiglottitis PA2 Surgical field adoidance during anaesthesia PA2 General anaesthesia in other than supine position PA2 Prolonged anaesthesia PA2 Bulbar neuromuscular disease PA2 Coma PA2 Stroke PA2 Drug overdose PA2 General anaesthesia for patient with full stomach PA2 General anaesthesia for parturient PA2 General anaesthesia for prolonged surgical procedures PA2 Neuromuscular diseases: PA2 Flail chest and lung contusion PA2 Pneumonia PA2 Respiratory failure PA2 Respiratory failure PA2 Paralysis PA2 Central nervous system trauma PA2 Anaesthesia for intrathoracic surgery
Quadriplegia PA3 Myasthenia gravis PA3 Ascending polyneuritis PA3 Neuromuscular disease PA3 Muscular relaxation for surgery
There are numerous ways to intubate a trachea, the choice of which depends on the preference of the anesthesiologist. For a patient with a normal airway, blind nasotracheal intubation in a spontaneously breathing awake patient has a good chance of success, yet the risk of causing upper airway bleeding may cause the anesthesiologist to turn to direct laryngoscopy. In any case, there are times when anesthesiologists are faced with management of difficult airway during intubation procedures.
Difficulty in intubation may be caused by one or more of the following: congenital facial and upper airway deformities, maxillofacial and airway trauma, airway tumors and abscesses, anatomical deformities in the nasopharyngeal or oropharyngeal region, the requirement for cervical spine immobility, fibrosis of the face and neck (burns or radiation), surgically induced deformities, and some systemic diseases. Attempts to push a endotracheal tube blindly through obstacles in the upper airway may result in excessive trauma and bleeding, possibly leading to severe glottic spasm or asphyxia. Bleeding prevents clear visualization of vocal cords, leading to further complication in the intubation process. Arthritis of temporomandibular joint or trismus limits the exposure of the patient's mouth, thus prevents the use of conventional direct laryngoscopy.
The management of the difficult airway may follow the algorithm shown in FIG. 1 of the drawings. Awake tracheal intubation is generally preferred. For an awake patient, the natural airway is better maintained and the muscle tone is enough to maintain the airway structure, which eases intubation.
Special techniques and instruments are required in managing the difficult airway. Since its first introduction in 1960, retrograde intubation, also referred as translaryngeal guided intubation, has been successfully used on patients with ankylosis of the jaw, cervical arthritis, tumors of the mouth and recently on patients with severe maxillofacial trauma. It is also an effective technique for securing the airway at an accident scene or in prehospital care of trauma patients, and for unexpectedly difficult intubation in operating theatres. The technique has a high success rate, is easy to learn and requires little practice. However, while apparatus for retrograde intubation is simple, it is not readily available in hospitals as there is no standardized equipment or procedure.
A planned retrograde intubation may be performed under local anaesthesia using light sedation and translaryngeal anaesthesia. A wide bore needle such as a 16 G Tuohy needle is used to puncture the cricothyroid membrane percutaneously towards cephalad (FIG. 2a). Air aspiration into a syringe filled with sterile water is used to confirm the position of the needle within the lumen of the larynx. Once the position is located, the syringe is removed and a guide (vascular guide wire or epidural catheter) is inserted through the needle (FIG. 2b) and threaded between the vocal cords into the pharynx. When an epidural catheter is used, it may coil up in the pharynx. The catheter may be spat out or retrieved from the patient's mouth by using Magill forceps (FIG. 2c). The needle is then withdrawn and the guide is secured at puncture site using a hemostat. For oral intubation, the endotracheal tube can be placed directly over the guide or a suction catheter can be passed over the original guide to provide a larger and stiffer guide for the tracheal tube (FIG. 2d). Once the top of the endotracheal tube reaches the cricothyroid membrane (FIG. 2e), the guide is released at the puncture site and is removed from above. The endotracheal tube is further advanced into the final position in the trachea (FIG. 2f).
If nasal intubation is intended, a soft plastic suction catheter is inserted through the nose into the pharynx and brought out through the mouth (FIG. 3). The tip of the retrograde catheter and the proximal end of the suction catheter are tied together with suture and the retrograde catheter is pulled back through the pharynx and out of the nose. In another approach employed by S. S. Dhara, one of the inventors of the present invention, a length is cut from the tip of the suction catheter and the epidural catheter is fed through the lumen of the suction catheter until it protrudes from the nasal end. The suction catheter is then completely retrieved to bring the epidural catheter out from the nose. The tracheal tube is then inserted over the retrograde catheter and into the larynx. The rest of the procedure is similar to that for orotracheal intubation.
Several variations of the apparatus and technique used in guided retrograde intubation have been employed in the prior art. These variations were designed and used to solve complications encountered during retrograde intubation. However, such prior art apparatus and technique all possess one or more deficiencies.
A relatively large and stiff endotracheal tube threaded over a soft catheter guide or a thin flexible fibreoptic endoscope in fibreoptic aided intubation may be diverted into the esophagus (FIG. 4), resulting in esophageal intubation. Long flexible tip retrograde guide wires such as the Seldinger type intravascular guide wire or teflon coated Swan-Ganz introducer wire provides better stiffness and control over an epidural catheter. However, discrepancy between the outer diameter of the guide wire and the inner diameter of the endotracheal tube may cause the endotracheal tube to move round the guide, causing the endotracheal tube to hang up on the glottis (FIG. 5), epiglottis and arytenoid cartilages.
Various techniques have been used for reproducible and successful guiding of the endotracheal tube into the trachea, including use of a stiffer retrograde guide, and by reduction of the discrepancy in diameters b enlarging the external diameter of the retrograde guide using an anterograde guide over it in a one-stop Seldinger type technique. Frozen suction catheter warmed-up plastic sheath stylet, cut gum elastic Eschmann stylet (FIG. 6), and fibreoptic bronchoscopes have been used. The type of anterograde guide used currently depends very much on the convenience and availability of the devices, and preference of individual anesthesiologist.
All of the foregoing anterograde guides have to stop at the point of puncture at the cricothyroid membrane. When the retrograde guide is completely withdrawn for further insertion of the endotracheal tube, the tube may dislodge from the laryngeal inlet, resulting in esophageal intubation. One of the modifications to prevent the dislodgement of endotracheal tube is to pass the guide through the "Murphy eye" of the tracheal tube (FIG. 7) to allow for an additional 1 cm of the endotracheal tube within the trachea prior to removal of the guide. In another approach, a gum elastic bougie (FIG. 8) was inserted through the tracheal tube and used as an anchor for further insertion of the tracheal tube. The disadvantage of this method is the inability to fit the gum elastic bougie through the tracheal tube and the anterograde catheter.
Breathholding and respiratory (inspiratory) obstruction may occur during the insertion of an epidural catheter and endotracheal tube. Sometimes, oxygen administration is necessary during intubation. Extra doses of topical local anaesthetic may be needed during the procedure to suppress the reflex arising from upper airway. An anterograde guide which allows continuous ventilation, measurement of airway pressure and respiratory gases, and application of local anaesthetic without disrupting the insertion of endotracheal tube would be extremely useful in such situations.
To the inventors' knowledge, there is only one kit marketed for retrograde intubation (Cook, Australia). Cook's retrograde guide wire is rather thick and stiff. The anterograde guide is a long, narrow single lumen tapered nylon tubing. The step or gradual tapering of the anterograde guide is a very important factor for guiding such as in intravascular catheterization where the Seldinger wire, dilator and sheath make a smooth cone. The discrepancy in diameters between the anterograde guide and the endotracheal tube leaves a large gap causing the endotracheal tube to be "caught" in the glottic inlet.
Little emphasis has been placed in the designing of an anterograde guide with regards to appropriate stiffness and diameter. The anterograde guide should be flexible enough to follow the retrograde guide along the curvatures of the upper airway. At the same time, it must have adequate stiffness for its primary function as an anterograde guide so as to avoid the endotracheal tube straying into the oesophagus.
Ventilation, monitoring of airway pressure or sampling of respiratory gases may be required during or immediately after the procedure of intubation. The "jet stylet" described by Bedger, et al. (1987) provides ventilation through a narrow long catheter which is inadequate for more than a few minutes. Measurement of airway pressure is very important while this mode of ventilation is employed, yet prior art apparatus makes no provision to facilitate such monitoring.
Administration of local anaesthetic into the upper respiratory tract during the procedure may be needed, yet again prior art devices do not readily accommodate such a requirement.
Anchoring of the anterograde catheter to prevent dislodgement of the endotracheal tube when the hold of the retrograde guide is being discontinued and the endotracheal tube is being negotiated through the laryngeal inlet is very important. However, there is currently no easily reproducible manoeuvre available to achieve this.